SSH – How to get `yum list` output to stay on one line when getting output via remote ssh command

pipesshterminalyum

When I SSH to a machine with ssh machine and run yum list it outputs everything that's installed as expected, and importantly every item is on one line like so:

xz-devel.i386                                                                                                        4.999.9-0.3.beta.20091007git.el5                                                                  base            
xz-devel.x86_64                                                                                                      4.999.9-0.3.beta.20091007git.el5                                                                  base            
xz-libs.i386                                                                                                         4.999.9-0.3.beta.20091007git.el5                                                                  base            
xz-lzma-compat.x86_64                                                                                                4.999.9-0.3.beta.20091007git.el5                                                                  base

But upon doing it remotely with ssh machine 'yum list' or even piping it to grep while on the server with yum list | grep xz -C 3 the output's lines are "truncated" and made much shorter, like so:

xz-devel.i386                              4.999.9-0.3.beta.20091007git.el5
                                                                       base     
xz-devel.x86_64                            4.999.9-0.3.beta.20091007git.el5
                                                                       base     
xz-libs.i386                               4.999.9-0.3.beta.20091007git.el5
                                                                       base     
xz-lzma-compat.x86_64                      4.999.9-0.3.beta.20091007git.el5
                                                                       base

How can I make the size of the line not shrink like this? My end desire is to pipe this to tee and then do some processing on the outputted file for all my hosts via ansible.

It seems that this is occurring due to some sort of "virtual terminal" as part of the SSH/piping because I can get the same behavior if I shrink my terminal size where the lines break when running yum list. Thus I'd assume that the addition of the pipe somehow tells yum list that the width of the terminal is only X columns

Best Answer

Per this answer provided in the comments by @thrig I was able to get it to output correctly by doing

yum list installed | xargs -n3 | column -t

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Bash – Use keyboard-interactive authentication when piping ssh output to other command

OK, it turns out this was due to a bizarre interaction with my bash configuration.

I have something in my .bash_profile that puts the currently executed command into the window title, or the screen tab. It works by using a trap:

trap 'bash_current_command' DEBUG

and before that:

function bash_current_command {
    # only works in bash > 3.1
    #set -- $BASH_COMMAND

    # for old bash
    set -- $(history 1)
    shift

    if [[ "$1" == "sudo" ]]; then
        cmd="*$(basename -- "$2")*"
    else
        cmd="$(basename -- "$1")"
    fi

    bash_set_title "$cmd"
}

bash_set_title is a little function that sets the current terminal's title and icon title using ANSI escape codes. As you can see, this creates subshells $(...), and my intuition told me this could be the problem. Indeed, after I changed those lines, it worked!

If someone knows why this happens, I'd be glad to hear details. Do subshells generally steal tty input? Or is it only a problem in a debug trap? I don't recall problems with regular stdin input / piping into commands.

(As you can also see, there are a few problems with my function anyway - it uses one of the subshells as a workaround so it can run on an archaic bash version (I'm stuck with it on a legacy system, but still wanted a unified configuration). The other subshell is used to extract the actual command when using sudo, but this fails if sudo is called with switches like sudo -H -u user command. So I'll regard this as an opportunity to fix up this code...)

Bash – SSH into a remote shell, execute a ‘source’ command, and stay in the remote shell

Use a new source file e.g. /home/user/.rcforssh

 #rc for ssh
 . /home/user/.bashrc
 . /home/user/venv/bin/activate  #or whichever location

and log in with

ssh -t user@host "cd /path/to/dir ; /bin/bash --rcfile /home/user/.rcforssh"

Side note: source is not POSIX, while . is.

UPDATE following discussion specifying OP's needs:

For creating and removing the the modified source file rcforssh on the fly, on can use:

ssh -t user@host "cd /path/to/dir ; echo '. ~/.bashrc ; . s ; rm rcforssh' > rcforssh ; /bin/bash --rcfile rcforssh"

i.e. creating the source file with an echo command and adding the removal in said file.

Best Answer

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Bash – Use keyboard-interactive authentication when piping ssh output to other command

Bash – SSH into a remote shell, execute a ‘source’ command, and stay in the remote shell

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